Hot-melt adhesives (HMAs) are generally solid materials at ambient temperature and can be heated to a melt to hold adherents or substrates together upon cooling and solidifying. Hot-melt adhesives offer the possibility of almost instantaneous bonding that make them excellent candidates for automated operations. HMAs can be used in paper products, packaging materials, and disposable goods, for example have many commercial applications.
Hot melt adhesives are widely used in the packaging industry to seal cardboard cases, trays and cartons. Many types of packaging applications require the use of an adhesive that is both heat resistant and cold tolerant. The hot melt adhesive used to seal the containers must have heat resistance and cold resistance particularly during transportation and storage. Sealed containers being transported and/or stored within a truck or rail car are exposed to very high temperatures in the summer (up to 75° C. or higher) and very low temperatures in the winter (down to −30° C. or lower). Thus, hot melt adhesives used in packaging applications need to be strong enough such that the sealed containers will not pop open during the transportation process.
HMAs are generally based on a polymer, a tackifier, and a wax. Fischer-Tropsch waxes (FT waxes) are commonly used as the wax component. Compared to other waxes (such as microcrystalline waxes and paraffin waxes), FT waxes have a higher melting temperature and a lower viscosity. FT waxes provide conventional HMAs with suitable heat resistance and adhesion performance for packaging applications.
FT waxes, however, are expensive and limit sourcing options for hot melt adhesive formulators. A need therefore exists for hot melt adhesive compositions, that meet the performance of conventional HMAs with FT wax, yet do not require a FT wax. A need further exists for such FT wax-free HMA compositions to exhibit both high temperature adhesive performance and low temperature adhesion performance.